1. Field of the Invention
An exemplary embodiment relates to a flat panel display device, and more particularly, to a transreflective liquid crystal display and a method of manufacturing the same.
2. Discussion of the Related Art
With development of information technology, the use of image display devices such as televisions, computer monitors and notebooks has been increased. Cathode ray tubes (CRTs) had been mainly used as the image display devices, but it is very difficult to manufacture them thinly and lightly.
Accordingly, the cathode ray tubes have been replaced by flat panel display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting device (OLED). Out of the flat panel display devices, the liquid crystal display has been widely used because the high resolution of the liquid crystal display can be achieved and the large-sized liquid crystal display as well as the small-sized liquid crystal display can be manufactured.
The liquid crystal display includes a color filter substrate, a thin film transistor substrate, and a liquid crystal layer interposed between the two substrates. The color filter substrate may include a first insulating substrate, a black matrix, and red, green, and blue color filters formed on the first insulating substrate. The thin film transistor substrate may include a second insulating substrate, a thin film transistor and a pixel electrode formed on the second insulating substrate. Herein the pixel electrode functions as a light transmissive electrode.
The liquid crystal display having the above-described configuration may be classified into a twisted nematic (TN) mode LCD, a vertically aligned (VA) mode LCD, and an in-plane switching (IPS) mode LCD depending on a manner for driving the liquid crystal layer. In the TN, VA, and IPS mode LCDs, the disposition and structure of electrodes for driving the liquid crystal layer are different from one another.
For instance, a common electrode for driving the liquid crystal layer is formed on the color filter substrate in the TN and VA mode LCDs, while the common electrode is formed on the thin film transistor substrate in the IPS mode LCD. Further, the common electrode is formed in the form of one plate in the TN mode LCD, while the common electrode is formed in the form of a plurality of plates in the IPS mode LCD. Furthermore, in the IPS mode LCD, each of the plates has a predetermined shape and is spaced apart from a neighboring plate at a predetermined interval.
The TN, VA, and IPS mode liquid crystal displays may be manufactured as a transreflective liquid crystal display. In the transreflective liquid crystal display, a plurality of sub-pixels constituting a unit pixel, namely, red, green, and blue color filters each includes a light transmitting area and a light reflective area. Therefore, the light transmitting area transmits light in a transmitting mode, and the light reflective area reflects and transmits light in a reflective mode.
The transreflective liquid crystal display includes a light reflective electrode formed at a location corresponding to the light reflective area, and the light reflective electrode is generally positioned on the thin film transistor substrate.
A principle in which a color of an image displayed by the transreflective liquid crystal display is achieved is schematically described as follows.
First, in the transmitting mode, after backlight light from a backlight unit on a rear surface of the transreflective liquid crystal display passes through the liquid crystal layer in the light transmitting area, the red, green, and blue color filters of the color filter substrate transmit the backlight light. The displayed image can represent various colors by carrying out additive mixture of color stimuli on the backlight light transmitted by the red, green, and blue color filters.
On the other hand, in the reflective mode, after the red, green, and blue color filters transmit external light such as solar light in the light reflective area, the external light passes through the liquid crystal layer and then is reflected by the light reflective electrode. After the external light reflected by the light reflective electrode again passes through the liquid crystal layer as well as the red, green, and blue color filters. The displayed image can represent various colors by carrying out additive mixture of color stimuli on the external light transmitted by the red, green, and blue color filters.
As described above, the red, green, and blue color filters once transmit the backlight light in the light transmitting area, the red, green, and blue color filters twice transmit the external light in the light reflective area. Therefore, light transmittance in the light reflective area is relatively reduced. Hence, luminance in the light reflective area is relatively lower than a luminance in the light transmitting area.